package com.anhry.app.safety.util;

import java.net.InetAddress;

/** 
 * 2010-4-8 
 * remark: 创建UUID编码
 * author:001 
 */
public class UUIDGenerator {

	private static final int IP;
	static {
		int ipadd;
		try {
			ipadd = BytesHelper.toInt(InetAddress.getLocalHost().getAddress());
		} catch (Exception e) {
			ipadd = 0;
		}
		IP = ipadd;
	}
	private static short counter = (short) 0;
	private static final int JVM = (int) (System.currentTimeMillis() >>> 8);

	public UUIDGenerator() {
	}

	/**
	 * Unique across JVMs on this machine (unless they load this class
	 * in the same quater second - very unlikely)
	 */
	private int getJVM() {
		return JVM;
	}

	/**
	 * Unique in a millisecond for this JVM instance (unless there
	 * are > Short.MAX_VALUE instances created in a millisecond)
	 */
	private short getCount() {
		synchronized (UUIDGenerator.class) {
			if (counter < 0)
				counter = 0;
			return counter++;
		}
	}

	/**
	 * Unique in a local network
	 */
	private int getIP() {
		return IP;
	}

	/**
	 * Unique down to millisecond
	 */
	private short getHiTime() {
		return (short) (System.currentTimeMillis() >>> 32);
	}
	private int getLoTime() {
		return (int) System.currentTimeMillis();
	}

	private String sep = "";

	private String format(int intval) {
		String formatted = Integer.toHexString(intval);
		StringBuffer buf = new StringBuffer("00000000");
		buf.replace(8 - formatted.length(), 8, formatted);
		return buf.toString();
	}

	private String format(short shortval) {
		String formatted = Integer.toHexString(shortval);
		StringBuffer buf = new StringBuffer("0000");
		buf.replace(4 - formatted.length(), 4, formatted);
		return buf.toString();
	}


    /**
     * 根据当前jvm的启动时间，IP地址，系统时间，类载入次数得到唯一32位长字符串
     * @return  唯一32位长字符串
     */
	public String generate() {
		return new StringBuffer(36)
			.append(format(getIP()))
			.append(sep)
			.append(format(getJVM()))
			.append(sep)
			.append(format(getHiTime()))
			.append(sep)
			.append(format(getLoTime()))
			.append(sep)
			.append(format(getCount()))
			.toString();
	}

}

